package com.jacklei.leetocde305;

import java.util.HashMap;
import java.util.HashSet;

/*
* 给你一个下标从 0 开始、严格递增 的整数数组 nums 和一个正整数 diff 。如果满足下述全部条件，则三元组 (i, j, k) 就是一个 算术三元组 ：

i < j < k ，
nums[j] - nums[i] == diff 且
nums[k] - nums[j] == diff
返回不同 算术三元组 的数目。



示例 1：

输入：nums = [0,1,4,6,7,10], diff = 3
输出：2
解释：
(1, 2, 4) 是算术三元组：7 - 4 == 3 且 4 - 1 == 3 。
(2, 4, 5) 是算术三元组：10 - 7 == 3 且 7 - 4 == 3 。
示例 2：

输入：nums = [4,5,6,7,8,9], diff = 2
输出：2
解释：
(0, 2, 4) 是算术三元组：8 - 6 == 2 且 6 - 4 == 2 。
(1, 3, 5) 是算术三元组：9 - 7 == 2 且 7 - 5 == 2 。


提示：

3 <= nums.length <= 200
0 <= nums[i] <= 200
1 <= diff <= 50
nums 严格 递增*/
public class Solution {
    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.arithmeticTriplets(new int[]{4,5,6,7,8,9}, 2));
    }
    public int arithmeticTriplets(int[] nums, int diff) {
        int ans = 0;
        HashSet<Integer> set = new HashSet<>();
        for (int num : nums) {
            set.add(num);
        }
        for (int i = 0; i < nums.length; i++) {
            int curI = nums[i];
            if(set.contains(curI+diff) && set.contains(curI+(diff*2)))
                ans ++;
        }
        return ans;
    }
}
